The invention relates to a method for sorting objects, especially pieces of mail, as well as to a sorting plant.
If objects have to be sorted in large numbers, as is especially the case with pieces of mail the form of packets, flats (periodicals, brochures etc.) or bundles, then devices are frequently employed for this purpose which are largely mechanized and automated, so that manual activities only remain to be carried out at specific points. The sorting plants feature a transport device on which the output objects to be sorted are conveyed according to predetermined sort criteria (especially address) by means of a transport device to one of a number of outputs of the sorting plant. At least one container is positioned at the respective output which accepts the object routed to this location and where necessary also collects further objects with the same sort criteria. At the end of a sorting process, or if during a sorting process a container has already reached a correspondingly high fill level, this container is transported away in each case and immediately replaced by an empty container, so that the sorting process can be continued or a new sorting process can be started. The completely or partly filled container can of course be taken away manually but also by means of automated conveyor systems. The provision of new containers can obviously also be undertaken manually. It is usual however to provide a special conveyor device in each case for delivering the containers to the outputs of the sorting plant to their placement positions, which has a corresponding space requirement and demands a not inconsiderable investment outlay.
Basically simple linear conveyor runs with switches or also plows for the individual outputs can be used as a sorting plant. However sorters, which are embodied for example as tilt tray sorters or especially as crossbelt sorters, are normally used as sorting plants. Corresponding plants are for example known from U.S. Pat. No. 6,478,138 B1, EP 0 811 567 B1 or U.S. Pat. No. 6,662,20. Such sorting plants mostly feature an endless transport device circulating in a horizontal plane for the items to be sorted. This means that an object once injected can also circulate repeatedly if necessary. However there are also sorters which have a circulating transport device, but this device runs in a vertical plane, so that a transport of objects is only possible in the horizontal sections of the circuit. To this extent such a plant behaves like a linear conveyor run with corresponding switches or plows for sorting objects. A sorting plant for letters which are sorted into mail containers is known from U.S. Pat. No. 6,561,339 B1. This plant features an automatic conveyor system fully independent from the transport system for the delivery of empty mail containers and for the removal of filled mail containers.
A device for removal of individual mail containers from a stack of mail containers stacked above one another is known from U.S. Pat. No. 6,846,153 B2.
Finally US 2005/0002772 A1 deals with a handling system for mail containers.